gistfile1.txt

data CurAppState = Login | Home | Other

app :: MonadWidget t m => CurAppState -> m ()
app Login = ...
app Home = ...
app Other = ...

navBar :: MonadWidget t m => m (Event t CurAppState)
navBar = do
    a <- button "Login"
    b <- button "Home"
    c <- button Other
    return $ leftmost [Login <$ a, Home <$ b, Other <$ c]

main = do
    ...
    stateChangeEvent <- navBar
    widgetHoldHelper app Login stateChangeEvent